Author:

Jonathan Menard(Princeton Plasma Physics Laboratory)

For magnetic fusion to be economically attractive and have near-term impact
on the world energy scene it is important to focus on key physics and
technology innovations that could enable net electricity production at
reduced size and cost. The tokamak is presently closest to achieving the
fusion conditions necessary for net electricity at acceptable device size,
although sustaining high-performance scenarios free of disruptions remains a
significant challenge for the tokamak approach. Previous pilot plant studies
have shown that electricity gain is proportional to the product of the
fusion gain, blanket thermal conversion efficiency, and auxiliary heating
wall-plug efficiency. In this work, the impact of several innovations is
assessed with respect to maximizing fusion gain. At fixed bootstrap current
fraction, fusion gain varies approximately as the square of the confinement
multiplier, normalized beta, and major radius, and varies as the toroidal
field and elongation both to the third power. For example, REBCO
high-temperature superconductors (HTS) offer the potential to operate at
much higher toroidal field than present fusion magnets, but HTS cables are
also beginning to access winding pack current densities up to an order of
magnitude higher than present technology, and smaller HTS TF magnet sizes
make low-aspect-ratio HTS tokamaks potentially attractive by leveraging
naturally higher normalized beta and elongation. Further, advances in
kinetic stabilization and feedback control of resistive wall modes could
also enable significant increases in normalized beta and fusion gain.
Significant reductions in pilot plant size will also likely require
increased plasma energy confinement, and control of turbulence and/or low
edge recycling (for example using lithium walls) would have major impact on
fusion gain. Reduced device size could also exacerbate divertor heat loads,
and the impact of novel divertor solutions on pilot plant configurations is
addressed. For missions including tritium breeding, high-thermal-efficiency
liquid metal breeding blankets are attractive, and novel immersion blankets
offer the potential for simplified fabrication and maintenance and reduced
cost. Lastly, the optimal aspect ratio for a tokamak pilot plant is likely a
function of the device mission and associated cost, with low aspect ratio
favored for minimizing TF magnet mass and higher aspect ratio favored for
minimizing blanket mass. The interplay between a range of physics and
technology innovations for enabling compact pilot plants will be described.

*This work was supported by U.S. DOE Contract Number DE-AC02-09CH11466

To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2016.DPP.TI3.4